I’ve been down a bit of a methylation rabbit hole lately, and it started, as most of my supplement reading does, with creatine. I stack creatine with a few other things and every so often I go back and check whether what I’m doing still holds up against the evidence. In that process I kept running into the same three letters: TMG. A few forums mentioned it alongside creatine, and a couple of the more research-minded accounts I follow brought it up too. So I went and read the actual studies instead of the marketing pages, and what I found was more interesting than I expected.
So, What Is TMG?
TMG stands for trimethylglycine. You’ll also see it labelled betaine, or betaine anhydrous, which is the same compound (not to be confused with betaine HCl, a completely different supplement used to support stomach acid for digestion). TMG occurs naturally in beetroot, spinach, and wheat bran, and the supplement form is usually made from sugar beet processing.
In the body, TMG works as a methyl donor. That means it hands off a small chemical group to other molecules so various bodily processes can run properly, including liver function, cell repair, and how the body clears a byproduct called homocysteine. More on that below.
The Research on Strength and Performance
This is the part that made me pay attention. There are a handful of trials worth knowing about, and none of them are huge, but they point in a fairly consistent direction.
The best-known study followed 29 academy-level soccer players (average age around 15 and a half) through a 14-week competitive season. The betaine group held on to their testosterone levels across the season, while the placebo group’s testosterone dropped. The betaine group also came out ahead on predicted one-rep max, VO2 max, and repeated sprint ability.
A smaller study looked at 10 adolescent handball players over just two weeks. After betaine, they managed noticeably more reps to fatigue on leg press and bench press, plus a better testosterone response and lower cortisol and lactate, following a single hard training session.
Then there’s a three-week trial in adult CrossFit athletes I find more relatable, since most of my readers aren’t teenage academy athletes. Betaine supplementation improved Fight Gone Bad style performance by around 8.7 per cent compared with no change on placebo, and testosterone rose by roughly 7 per cent. It made no difference to Wingate anaerobic power or body composition.
An earlier six-week study in experienced strength-trained men found something slightly different again: betaine improved body composition and bench press training volume, but didn’t reach statistical significance for actual strength gains.
I’ll say this plainly: this research base is still small, still short-term, and often in younger or very specific groups of athletes. It’s not a settled area of sports science. But for something this cheap and well tolerated, it’s a genuinely interesting one to keep an eye on, and it’s given me a good reason to try it myself.
The Creatine Connection
If you already take creatine, this bit is relevant. Creatine metabolism produces homocysteine as a byproduct. Elevated homocysteine has been linked to cardiovascular risk, and a major Lancet review in 2020 named it as a risk factor for cognitive decline. TMG is one of the ways the body clears homocysteine, converting it back into methionine through methylation.
So when people stack TMG with creatine, they’re not just stacking one performance boost on another. They’re managing a byproduct that creatine itself produces, even though the research above suggests TMG might do a bit of both jobs at once. For anyone already on creatine, TMG is more of a “tidying up after yourself” addition than a whole new supplement category.
How Much and When
Doses used in research range from 500 mg up to 2,000 mg a day, with most trials sitting between 1,000 mg and 2,000 mg. If you’re starting out, 1,000 mg with a meal is a sensible place to begin, and you can build from there if you want to.
One thing worth flagging: doses above 4 g a day have been associated with small rises in total cholesterol in some studies. That’s not a reason to avoid TMG altogether, but it’s a reason to stick to researched doses and speak to your GP first, especially if you have an existing cardiovascular condition. I say this about most supplements I cover, but it matters a bit more here given the range of doses involved.
Where to Find TMG
I don’t tend to rank supplement brands, so here’s what I’d point my own readers to, depending on where you’re based.
In the UK, NOW Foods TMG tablets are available through Amazon UK, and NOW is one of the more established names in the sports nutrition space.
In the US, NOW Foods also does a TMG betaine anhydrous range in both powder and capsule form, widely stocked through US supplement retailers and Amazon. Worth clearing up while I’m here: if you go looking for a well-known “betaine” product from Thorne, you’ll find Betaine HCl & Pepsin, which is a different supplement altogether, aimed at digestion and stomach acid rather than methylation. Don’t mix the two up when you’re shopping.
In Canada, Nutravea TMG (trimethylglycine) is a straightforward option: 750 mg per capsule, 240 capsules per bottle, prepared in Canada and Health Canada licensed. The per-capsule dose makes it easy to build up to a full serving without swallowing a handful of pills.
None of these is “the one to get.” They’re simply options for wherever you happen to be reading this from.
TMG isn’t going to replace consistent training, proper sleep, and a diet that actually supports your goals, and it was never going to be that kind of supplement. But if you’re already training properly and you’re curious about the smaller things that might help, this is one of the more genuinely interesting additions I’ve come across in a while. The evidence is promising rather than proven, it’s well tolerated at sensible doses, and it costs next to nothing compared with most of what’s sitting on supplement shop shelves. That’s a fairly rare combination, and it’s why I wanted to write about it.
Elle
